This invention relates generally to broadband communications systems, such as cable television systems, and more specifically to an extended interface module used in headend racks that is suitable for use in the broadband communications systems.
A broadband communications system 100, such as a two-way hybrid/fiber coaxial (HFC) communications system, is depicted in FIG. 1. Such a system may be used in, for example, a cable television network; a voice delivery network, such as a telephone system; and a data delivery network to name but a few. The communications system 100 includes headend equipment 105 for generating forward signals (e.g., voice, video, or data signals) that are transmitted in the forward, or downstream, direction along a first communication medium, such as a fiber optic cable 110. Coupled to the headend 105 are optical nodes 115 that convert the optical signals to radio frequency (RF) signals. The RF signals are further transmitted along a second communication medium, such as coaxial cable 120, and are amplified, as necessary, by one or more distribution amplifiers 125 positioned along the communication medium. Taps 130 included in the communications system split off portions of the forward signals for provision to subscriber equipment 135, such as set-top terminals, computers, telephone handsets, modems, and televisions. It will be appreciated that only one fiber link connecting the headend 105 with a node 115 is shown for simplicity; however, there are typically several different fiber links connecting the headend 105 with several additional nodes 115, amplifiers 125, and subscriber equipment 135.
In a two-way system, the subscriber equipment 135 can also generate reverse electrical signals that are transmitted upstream to the headend equipment 105. Such reverse signals may be amplified by any one or more of the distribution amplifiers 125 and converted to optical signals by the optical node 115 before being provided to the headend equipment 105.
In a typical headend facility, the necessary equipment for signal processing comprises a significant number of modulators, demodulators, upconverters, and power supplies to name but a few. By way of example, a communications system may deliver 132 stereo channels of broadband video and audio to subscriber equipment that originates from the headend facility. The required headend equipment for 132 stereo channels may be, for example, housed in 8 racks each with 32 chassis for a total of 256 chassis. FIG. 2 illustrates one such rack 205 having 32 chassis. Spaces 210 are left in between the equipment rows for air circulation and extensive cabling is routed in the back of the racks A (not shown). The additional 7 racks (not shown) are situated tightly against the illustrated rack 205.
Due to all the required racks for the headend equipment, the headend facility is typically limited in physical space. This space constraint may pose costly problems for the operator. More specifically, operators may be upgrading existing services and adding more channels to the current channel lineup. As a result, more equipment will be required in the headend facility. Consequently, some operators may have to move their headend equipment to a larger facility to accommodate the newly required equipment. What is needed, therefore, are modules that allow the operator to design a more efficient layout of the headend facility using existing racks rather than the conventional layout using the conventional headend equipment.